Crystal detector for radioreception



Sept. 16,1924. 1,508,893

F. G. MITCHELL CRYSTAL DETECTOR FOR RADIORECEPTION Filed June 24, 1922 INVENTOR FredericK G1 Milrhell BY his ATTORNEY Patented Sept. 16, 1924,

MNHTED STATES rarest @FEHQE.

FREDERICK e. MITCHELL, or nrnenrrnnn PARK, JERSEY.

' CRYSTAL nnrneron FOR iannroanonrr on.

Application filed June 24, 1922. Serial No. 570,533.

To all whom it may concern: I Be. it known that I, FREDERICK G. MITCHELL, a citizen of the United States, residing at Ridgefield Park, county of Bergen, and State of New Jersey, have invented a new and useful Crystal Detector for Radioreception, of which the following is a specification.

My invention relates to improvements in detectors for radio reception, in which a crystal is employed to complete the circuit, and it consists in the novel features hereinafter more fully described.

The objects of my improvement are: First: to avoid the annoyance and loss of time due to the delicate adjustment, which is required with the cat-whisker detectors at present in use;

Second: to make the crystal detector ready for use irrespective of any films, which may be formed on it by handling it; Third: to provide a crystal detector, the points of which may be readily sharpened; Fourth: to provide a crystal detector for radio reception which is considerably more sensitive than the detectors at present in use; Fifth: to provide a detector, a number of which may be placed into a circuit, without the necessity of any switches; and

radio reception simple, durable and inexpensive.

I attain these objects by the detector, one form of which is illustrated in the accompanying drawings or by any mechanical equivalents or obvious modifications of the same.

In the drawings Fig. 1 is a vertical section on the broken line 11111-1 of Fig. 2; Fig. 2 is a plan of my detector with the crystal omitted for the sake of clearness.

Fig. 3 is a side elevation, looking from right to left in Fig. 2.

Similar numerals refer to similar parts throughout the several views.

11 designates the base of my detector, which base may be made of a suitable com position material; 1212 are a pair of supports for the binding posts 13, which carry at their lower ends the nuts or rivets 13.

14-14 is a pair of plates, each of which is in electrical connection with a radio circuit, said plates being placed opposite to each other in a somewhat inclined position,

mediately. Sixth: to make my crystal detector for as shown in Fig. 1; each of the plates 14 is partly embedded in the base 11 and has at its lower end the horizontal extension 15, which is connected to one of the binding posts 13 by means of said nut or rivet 13 The upper edges of said plates 14-14 are formed preferably into saw teeth 16, which may readily be sharpened by a file.

The space between the saw teeth may be bridged by the crystal 17, thereby completing the circuit.

I found that the crystal 17 readily gets into contact with the saw teeth 16 after rolling it on thereto.

I also found that the result is much better than with cat whisker detectors, the radio being much louder and the crystal is not materially affected by any films due to the handling of the crystal.

In general my plate detector is much more substantial and sturdy than the cat whisker detector; no time has to be lost in manipulating the same. A number of these plate detectors may be placed in the circuit; no switches are required; all that is required to do is: to place the crystal on the upper edges of the pair of plates.

Signals can then be obtained almost im- The crystal may be handled withv the naked fingers without reducing its efi'iciency.

Instead of being saw toothed the upper edges of the plates 14 may be notched or fluted orserrated in any other way.

As an inferior substitute a number of needle points or sharp pins may be driven through or otherwise fastened to the plates 14 at the upper edges thereof and the crystal laid across these points,'for closing the circuit.

The crystal may even be placed across the sharpened upper edges of the plates 14;, without any teeth or points being provided thereon, and the circuit completed in this way; only the action is more perfect with the teeth 16 on the said plates 14 than without them.

Many other changes may be made in the details of my crystal detector for radio reception without departing from the main scope of my invention.

I do not, therefore. restrict myself to the details as shown; but I intend to include also all mechanical equivalents and reasonably obvious modifications of the same Within the scope of my invention.

What I claim as my invention, and desire to secure by Letters Patent is:

1. In a crystal detector for radio reception a base and a pair of plates connected thereto, each of said plates being in electrical connection with a radio circuit, and said plates having a pair of serrated edges situated opposite each other, combined With a crystal placed in contact with the serrations, of said edges, thereby completing the circuit,

2. In a crystal detector for radio reception a base and multiple serrated bodies connected thereto, each of said bodies being in electrical connection With a radio circuit and the serrations of said bodies being situated opposite each other, combined with a crystal placed in contact With said serra- 20 tions, thereby completing the circuit,

FREDERICK G. MITCHELL, 

